The invention relates to circular clarifiers, and more particularly, to sludge collectors used in circular clarifiers.
Circular clarifiers typically include a tank, a center pier, and a sludge collector. The tank is cylindrically shaped and is capable of containing a solution. The center pier projects from the bottom of the tank along a central axis and includes inlet ports. A solution containing suspended solids is supplied to the center of the tank from the inlet ports such that the solution gradually moves radially outwardly toward the wall of the tank. As the solution flows outwardly, solids settle from the solution onto the tank floor thereby separating the solids from the solution. The clarified liquid is removed from the tank through outlet ports located along the tank wall near the surface of the solution.
Sludge collectors retrieve the sludge that settles from the solution onto the bottom of the tank. Sludge collectors typically include a withdrawal manifold and a scraper assembly. The withdrawal manifold is centrally mounted for rotation about the center pier. The scraper assembly is generally spiral-shaped such that rotation of the scraper assembly moves the settled sludge toward the center of the tank and into the withdrawal manifold where it is removed by a sludge withdrawal line.
The present invention is directed to an entrapment plate that provides a physical barrier for trapping transported sludge between the withdrawal manifold and the scraper assembly and funneling the trapped sludge into the withdrawal manifold of the sludge collector. The entrapment plate of the present invention minimizes the carryover of concentrated sludge over the scraper assembly by providing a physical barrier that holds the sludge below the height of the scraper assembly instead of solely relying on small differences in the specific gravities of different sludge concentrations to hold the sludge in front of the scraper assembly. The entrapment plate also allows the size of the withdrawal ports to be increased, thereby decreasing the exit velocity through the withdrawal ports and minimizing the infusion of lesser concentrated sludge into the rotating withdrawal manifold.
One embodiment of the present invention is directed to a sludge collector for use with a circular clarifier. The circular clarifier includes a tank that has a bottom and a wall that extends upwardly from the bottom of the tank. The tank is configured to contain a solution and allow sludge to settle from the solution to the bottom of the tank. The sludge collector includes a withdrawal manifold, a scraper assembly, and an entrapment plate. The withdrawal manifold is located at the bottom of the tank. The scraper assembly extends from the withdrawal manifold toward the wall of the tank and moves the settled sludge toward the withdrawal manifold. The entrapment plate extends between the withdrawal manifold and the scraper assembly to trap sludge between the withdrawal manifold and the scraper assembly and funnels the trapped sludge into the withdrawal manifold.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.